Fluid vehicle dampers, such as hydraulic shock absorbers and struts, provide a smooth ride by absorbing forces that are generated by an uneven road surface. Two common types of vehicle fluid dampers are monotube and twin tube shock absorbers, each of which have a cylinder and piston. Twin tube shock absorbers have a valve body located at an end of the piston, commonly referred to as a piston valve, and at a cylinder end, commonly referred to as a base valve. The piston valve moves toward the base valve during compression of the shock absorber and moves away from the base valve during rebound. The valve bodies divide the shock absorbers into several fluid chambers and regulate the flow of fluid from one chamber to another thereby achieving particular ride handling characteristics. Typically, each valve body has a compression and rebound valve assembly located on opposing surfaces of the valve body that regulate fluid flow during the compression and rebound strokes. By modifying the valve assemblies, the ride handling characteristics may be calibrated.
Typically, it may be desirable to have a low speed bypass valve and a high speed bypass valve as part of a valve assembly to provide different degrees of damping depending on the speed at which the shock absorber compresses or rebounds. The valve bodies have inner and outer annular seats that coact directly or indirectly with adjacent low and high speed bypass valves. During low speed movement of the piston, such as vehicle cornering maneuvers, fluid only flows past the low bypass valve while the high bypass valve remains closed. Thus, the low speed bypass valve provides a rate of damping. One prior art low speed bypass valve has incorporated a solid disc-shape structure in abutting relation with the annular seats. The annular seats are coined to form notches through which the fluid may flow during low speed movement of the piston. However, the coining operation requires a library of precision tools to form the notches, which adds cost to the low speed bypass valve. Another prior art low speed bypass valve has incorporated a disc having notches at the perimeter of the disc adjacent to the outer annular seat. When the disc is adjacent to the annular seats, the fluid only flows through the notches in the disc during low speed movement of the piston. However, this type of disc tends to fatigue over time. Therefore, what is needed is a robustly designed low speed bypass valve that is inexpensive.